A mobile communication system includes a plurality of base stations, and each base station provides wireless access to terminals within a limited geographical area. An area covered by each base station is called a cell. In order to secure mobility of a terminal, a terminal moving between cells performs a handover. In this case, each base station may retain information about neighbor cells and provide the information to terminals. The information about neighbor cells includes a list of neighbor cells to which a handover from a relevant cell can be performed.
An LTE (Long Term Evolution) system being the next-generation communication system defines an SON (Self Organizing Network). The SON is a technology that supports self configuration, self optimization, self healing, and the like by applying a concept of artificial intelligence to a base station, thereby increasing the operation efficiency and communication quality of the base station and reducing operation/maintenance costs. An ANR (Auto Neighbor Relation) is a portion of the SON function, which automatically detects a neighbor cell and configures and optimizes an NRT (Neighbor Relation Table). When the ANR function is applied, the base station recognizes a change of installation or elimination of a new cell during an operation and reflects the cell installation or elimination on the NRT, thereby maintaining an optimal NRT.
However, the ANR function has the following problems. First, a delay may occur in the process where addition/deletion of an NR to/from the NRT occurs repeatedly within a short time during an ANR function operation, and thus a handover may fail. When a UE (User equipment) generates a measurement report on a new NR, the ANR function adds a new NR. However, when the NRT is in a size full state, the ANR function selects one of the existing NRs, deletes the selected NR from the NRT, and adds a new NR to the NRT. Thus, when a measurement report of a UE is generated repeatedly in an NRT size full state, the addition/deletion of an NR to/from the NRT is performed repeatedly. Therefore, a delay occurs in the process of adding a new NR, and thus a handover failure probability increases. Second, in handover performance respect, even an invalid NR may remain in the NRT. Even an NR having a low handover success rate may be a handover target of the UE until deletion by an operator, because it exists in the NRT without classification. When the UE attempts a handover to the NR having a low handover success rate, a handover failure probability increases and thus system performance degradation may occur.
What is therefore required is an alternative scheme for efficiently managing a neighbor cell list without the above-described problems.